This removes unparsed name resolution during the semantic
check because it feels like a hack to work around limitations
in the language syntax, that should be solved at the lexical
level instead.

We were interpreting unparsed differently on the LHS and RHS.
Now an unparsed value is always a field if it matches a
registered field name (this matches the implementation in 3.6
and before).

This requires tightening a bit the allowed filter names for
protocols to avoid some common and potentially weird conflicting
cases.

Incidentally this extends set grammar to accept all entities.
That is experimental and may be reverted in the future.